Firefighters, emergency response personnel, members of the military, racing personnel, and industrial workers that can be exposed to flames, high temperatures, and/or electrical arcs and the like, need protective clothing and articles made from thermally resistant fabrics. Any increase in the effectiveness of these protective articles, or any increase in the comfort or durability of these articles while maintaining protection performance, is welcomed.
A fiber known as polysulfonamide fiber (PSA) is made from a poly (sulfone-amide) polymer and has good thermal resistance due to its aromatic content and also has low modulus, which imparts more flexibility to fabrics made from the fiber; however, the fiber has low tensile break strength. This low tensile strength in fibers has a major impact on the mechanical properties of fabrics made from these fibers, with the most obvious result being a decrease in the durability of the fabrics and articles made from the fabrics. This low durability limits the ability to utilize this comfortable fiber in protective apparel, especially in firefighters' turnout coats that must function in extreme environments. Therefore what is needed is a way of incorporating PSA into yarns for use in protective apparel that utilizes the benefits of the PSA fiber while compensating for the limitations of the fiber.